From 7945af700da8a9d0f59c2c5f203217ca8c584ab2 Mon Sep 17 00:00:00 2001 From: Matt Corallo Date: Sun, 21 Jul 2024 23:29:19 +0000 Subject: [PATCH] [block-sync] Don't hold client-cache lock while connecting `lightning-block-sync`'s REST and RPC clients both hold a cache for a connected client to avoid the extra connection round-trip on each request. Because only one client can be using a connection at once, the connection is `take()`n out of an `Option` behind a `Mutex` and if there isn't one present, we call `HttpClient::connect` to build a new one. However, this full logic is completed in one statement, causing a client-cache lock to be held during `HttpClient::connect`. This can turn into quite a bit of contention when using these clients as gossip verifiers as we can create many requests back-to-back during startup. I noticed this as my node during startup only seemed to be saturating one core and managed to get a backtrace that showed several threads being blocked on this mutex when hitting a Bitcoin Core node over REST that is on the same LAN, but not the same machine. --- lightning-block-sync/src/rest.rs | 3 ++- lightning-block-sync/src/rpc.rs | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/lightning-block-sync/src/rest.rs b/lightning-block-sync/src/rest.rs index 9473f7b1b..74837f08f 100644 --- a/lightning-block-sync/src/rest.rs +++ b/lightning-block-sync/src/rest.rs @@ -34,7 +34,8 @@ impl RestClient { { let host = format!("{}:{}", self.endpoint.host(), self.endpoint.port()); let uri = format!("{}/{}", self.endpoint.path().trim_end_matches("/"), resource_path); - let mut client = if let Some(client) = self.client.lock().unwrap().take() { + let reserved_client = self.client.lock().unwrap().take(); + let mut client = if let Some(client) = reserved_client { client } else { HttpClient::connect(&self.endpoint)? diff --git a/lightning-block-sync/src/rpc.rs b/lightning-block-sync/src/rpc.rs index 8032d3fcc..59c7e589e 100644 --- a/lightning-block-sync/src/rpc.rs +++ b/lightning-block-sync/src/rpc.rs @@ -77,7 +77,8 @@ impl RpcClient { "id": &self.id.fetch_add(1, Ordering::AcqRel).to_string() }); - let mut client = if let Some(client) = self.client.lock().unwrap().take() { + let reserved_client = self.client.lock().unwrap().take(); + let mut client = if let Some(client) = reserved_client { client } else { HttpClient::connect(&self.endpoint)? -- 2.39.5